1. Field of the Invention
The present invention relates to a lead-free frit glaze having excellent gloss and cooling resistance.
2. Description of the Related Arts
Ceramics are conventionally produced by firing natural clay and/or pottery at high temperature. Generally, clay is first mixed with water and subjected to grinding and kneading. The clay-water mixture is then filtered to reduce the amount of water contained therein, resulting in the formation of a base body. The base body is subjected to biscuit firing to provide a biscuit base, and is coated with a frit glaze. After glost firing, the glazed ceramic article obtained is cooled. The frit glaze is coated on the surface of the ceramic to improve its surface gloss, water resistance, and cooling resistance.
Conventional frit glazes contain lead (Pb) in an amount ranging from several percent to over 10% by weight because it is easily vitrified due to its low melting temperature. Further, lead has excellent flow properties which facilitate the above described process for manufacturing ceramics. Lead also improves the coloring and gloss of the ceramic surface after firing.
Unfortunately, in order to produce the above-described frit glaze, red lead or white lead are indispensable ingredients. These materials are hazardous in that they cause air pollution. Moreover, the contact of only a very small amount of these lead ingredients with the drainage water and spray water used during glaze application is unavoidable, resulting in water contamination. Clearly, the development of a lead-free frit glaze which would avoid such pollution is desired in this art.